CN108159880B - Flue gas denitration system - Google Patents
Flue gas denitration system Download PDFInfo
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- CN108159880B CN108159880B CN201810019255.0A CN201810019255A CN108159880B CN 108159880 B CN108159880 B CN 108159880B CN 201810019255 A CN201810019255 A CN 201810019255A CN 108159880 B CN108159880 B CN 108159880B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/90—Injecting reactants
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8631—Processes characterised by a specific device
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8696—Controlling the catalytic process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/88—Handling or mounting catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L15/00—Heating of air supplied for combustion
- F23L15/04—Arrangements of recuperators
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/20—Reductants
- B01D2251/206—Ammonium compounds
- B01D2251/2062—Ammonia
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Chimneys And Flues (AREA)
Abstract
The invention discloses a flue gas denitration system, which comprises a flue gas input channel, an air preheater, a high-temperature electric precipitator, an SCR reactor and a mixed main pipe connected with the SCR reactor, wherein the air preheater, the high-temperature electric precipitator and the SCR reactor are sequentially connected to the flue gas input channel; the air preheater is divided into a high-temperature area, a medium-temperature area and a low-temperature area in sequence, and one end of the flue gas input channel enters from the high-temperature area and penetrates out from the medium-temperature area. The temperature of the flue gas discharged from the middle temperature zone is between 320 and 420 ℃, and the temperature is favorable for denitration treatment of the SCR reactor; and the flue gas from the SCR reactor is subjected to cooling treatment in a low-temperature area and finally discharged. The installation of a flue gas heating device and a flue gas cooler can be omitted through the arrangement, so that the energy consumption is saved, the environment is protected, and the operation cost is reduced.
Description
Technical Field
The invention relates to the technical field of waste gas treatment, in particular to a flue gas denitration system.
Background
In the prior denitration process, the air preheater 1 and the SCR denitration reactor 13 are separate and are relatively two independent devices. As shown in fig. 1, the temperature of the flue gas coming out of the boiler after heat exchange in the air preheater 1 is greatly reduced, the temperature of the flue gas before entering the air preheater 1 is generally above 1000 ℃, and the outlet temperature of the air preheater 1 is generally around 200 ℃. The flue gas from the air preheater 1 is sent to a dust collector 11 for dust removal and then sent to an SCR denitration reactor 13. At this time, in order to ensure that the temperature of the denitration reaction zone can be in a proper temperature range (320-420 ℃), so that the temperature of the flue gas entering the SCR denitration reactor 13 meets the requirement, the flue gas needs to be reheated, and a flue gas heating device 12 is usually arranged in an inlet flue of the SCR denitration reactor 13; after the flue gas is subjected to denitration reaction, in order to avoid thermal pollution of high-temperature flue gas to air and perform cooling treatment on the flue gas, a flue gas cooler 14 is arranged at the outlet of the flue of the SCR denitration reactor 13, so that denitration can be smoothly performed.
Like this the flue gas heating device 12 and the flue gas cooler 14 that set up in SCR denitration reactor 13 can increase extra energy consumption and investment, are unfavorable for energy-concerving and environment-protective, have also increased the operation cost of enterprise simultaneously.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a flue gas denitration system which can save the installation of a flue gas heating device and a flue gas cooler, thereby saving energy consumption, being beneficial to environmental protection and reducing the operation cost.
In order to achieve the purpose, the invention provides the following technical scheme: a flue gas denitration system comprises a flue gas input channel, an air preheater, a high-temperature electric precipitator, an SCR reactor and a mixing main pipe connected with the SCR reactor, wherein the air preheater, the high-temperature electric precipitator and the SCR reactor are sequentially connected to the flue gas input channel; the air preheater is sequentially divided into a high-temperature area, a medium-temperature area and a low-temperature area, and one end of the flue gas input channel enters from the high-temperature area and penetrates out from the medium-temperature area; one output end of the SCR reactor is connected with a flue gas output channel, and the middle section of the flue gas output channel passes through a low temperature region.
Through adopting above-mentioned technical scheme, when the flue gas temperature in the air preheater reduced to between 320 degrees centigrade to 420 degrees centigrade, just in time can follow the flue gas input channel and derive from the air preheater, and the temperature of flue gas just in time does benefit to the SCR reactor and carries out denitration treatment to this part flue gas this moment. Because the temperature of the flue gas before entering the SCR reactor is higher, a high-temperature electric dust remover is adopted. And the flue gas after denitration is subjected to heat exchange through a low temperature region along the flue gas output channel, and the final temperature of the flue gas is 120-180 ℃. Through the setting, the control on the temperature of the flue gas is more reasonable, and the original flue gas heating device and the original flue gas cooler can be omitted, so that the energy consumption is saved, the environmental protection is facilitated, and the operation cost is reduced.
The invention is further provided with: a first temperature switch device is arranged on a flue gas input channel between the high-temperature electric dust remover and the air preheater, the first temperature switch device comprises a first temperature sensor, a first controller and a first electric valve, the first temperature sensor is used for detecting the temperature in the flue gas input channel and transmitting a temperature signal to the first controller, and the first controller responds to the temperature signal of the first temperature sensor and is used for controlling the opening and closing of the first electric valve; the flue gas input channel is connected with a first transmission pipe, two ends of the first transmission pipe are respectively connected to two ends of the first temperature switch device, the middle section of the first transmission pipe is located in the medium-temperature area and is arranged close to the high-temperature area, and the first transmission pipe is provided with a first safety valve.
By adopting the technical scheme, when the temperature of the flue gas in the flue gas input channel is lower than 320 ℃, the first temperature sensor sends a temperature signal to the first controller, so that the first controller controls the first electric valve to cut off the flue gas input channel, the pressure in the flue gas input channel is increased, the first safety valve is opened, and the flue gas with the temperature lower than 320 ℃ returns to the part of the middle temperature zone close to the high temperature zone. Because the part of the middle temperature zone close to the high temperature zone can be used for heating the flue gas, the temperature of the flue gas is increased to be higher than 320 ℃, and then the flue gas returns to the flue gas input channel and is conveyed to the high temperature electric dust collector and the SCR reactor.
Because the temperature of the flue gas can often have some fluctuations, the temperature of the flue gas output to the outer side of the air preheater can be lower than 320 ℃, and the temperature of the flue gas input into the SCR reactor can be continuously higher than 320 ℃ through the arrangement, so that the denitration reaction of the SCR reactor is facilitated.
The invention is further provided with: a second temperature switch device is arranged on the flue gas input channel between the high-temperature electric dust remover and the air preheater, the second temperature switch device comprises a second temperature sensor, a second controller and a second electric valve, the second temperature sensor is used for detecting the temperature in the flue gas input channel and transmitting a temperature signal to the second controller, and the second controller responds to the temperature signal of the second temperature sensor and is used for controlling the opening and closing of the second electric valve; the flue gas input channel is connected with a second transmission pipe, two ends of the second transmission pipe are respectively connected to two ends of a second temperature switch device, the middle section of the second transmission pipe is located in the middle temperature area and is arranged close to the low temperature area, and a first safety valve is installed on the second transmission pipe.
By adopting the technical scheme, when the temperature of the flue gas in the flue gas input channel is higher than 420 ℃, the second temperature sensor sends a temperature signal to the second controller, so that the second controller controls the second electric valve to cut off the flue gas input channel, the pressure in the flue gas input channel is increased, the second safety valve is opened, and the flue gas with the temperature higher than 420 ℃ returns to the part of the middle temperature zone close to the low temperature zone. Because the part of the middle temperature zone close to the low temperature zone can be used for reducing the temperature of the flue gas, the temperature of the flue gas is reduced to be lower than 420 ℃, and then the flue gas returns to the flue gas input channel and is conveyed to the high temperature electric dust collector and the SCR reactor.
Because the temperature of the flue gas can often have some fluctuations, the temperature of the flue gas output to the outer side of the air preheater can be higher than 420 ℃, and the temperature of the flue gas input into the SCR reactor can be continuously lower than 420 ℃ through the arrangement, so that the denitration reaction of the SCR reactor is facilitated.
The invention is further provided with: and one output end of the SCR reactor is connected with a flue gas analyzer, and the mixing main pipe is connected with a dilution fan.
By adopting the technical scheme, NH inevitably exists in the operation of the SCR denitration system3Escape problem, escaping NH3With SO in flue gas3With steam to form NH4HSO4。NH4HSO4The flue gas is liquid within the temperature range of 146-207 ℃, the temperature of the flue gas is reduced after the flue gas passes through the low-temperature regions of the SCR reactor and the air preheater, and gaseous NH generated in the flue gas is reduced to below 185 DEG C4HSO4Solidification occurs, the temperature range between 140 ℃ and 230 ℃ is positioned in the low temperature region of the conventional design of the air preheater due to NH4HSO4In the temperature interval ofThe liquid state is converted into the solid state, and the high adsorbability can cause a large amount of ash to settle in the air preheater, cause the air preheater to block and the resistance to rise, and force the furnace to be shut down to clean the air preheater in serious cases. At the same time, NH4HSO4The catalyst has strong corrosiveness to metal, and can cause the corrosion of a catalyst metal support frame and a low-temperature area of the air preheater.
When NH is present3At a lower slip, NH4HSO4Will also be reduced, and too much ammonia gas introduced into the SCR reactor from the mixing main pipe will directly result in NH3The increase in slip is critical to control the amount of ammonia gas fed to the SCR reactor. The flue gas analyzer in the arrangement can detect the ammonia nitrogen ratio in the flue gas discharged by the SCR reactor, so that the condition that the ammonia gas is introduced too much or too little can be known, and the occupied ratio of the ammonia gas in unit volume introduced into the SCR reactor can be controlled by controlling the dilution fan.
The invention is further provided with: and a heat exchange air pipe is arranged in the air preheater, the heat exchange air pipe penetrates out of the high-temperature area to form an air outlet section, the heat exchange air pipe penetrates out of the low-temperature area to form an air inlet section, and the air inlet section is connected with a fan heater.
By adopting the technical scheme, after the air preheater enters winter, the environmental temperature is reduced, so that the exhaust gas temperature of the boiler is further reduced, the exhaust gas temperature is extremely easy to reach or be lower than the acid dew point, the low-temperature corrosion of the low-temperature area of the air preheater is induced, and the pollution and blockage of the air preheater are aggravated. The air heater in the arrangement can improve the temperature of the flue gas entering the low-temperature area of the air preheater and reduce the probability of low-temperature corrosion.
The invention is further provided with: a plurality of ammonia injection grids are installed in the SCR reactor, and a connecting pipe is connected between each ammonia injection grid and the mixing main pipe.
Through adopting above-mentioned technical scheme, along the direction of motion of flue gas in the SCR reactor, establish a plurality of ammonia injection grids, can improve the even degree that the ammonia gas scatters to in the SCR reactor.
The invention is further provided with: and a flow equalizing plate is arranged in the SCR reactor.
By adopting the above technologyTechnical solution, flow equalization plate is used for making ammonia and NOXThe mixture reaches the catalyst more uniformly, thereby improving the reaction quality per unit volume of the catalyst.
The invention is further provided with: the flue gas output channel extends low temperature district one end and is connected with the absorption tower, is connected with delivery pipe and delivery pipe on the absorption tower and keeps away from absorption tower one end and is connected with the chimney, installs the draught fan on the delivery pipe.
By adopting the technical scheme, the absorption tower is used for carrying out desulfurization treatment on the flue gas so as to reduce the sulfur content of the flue gas discharged to the atmosphere.
The invention is further provided with: and a heat exchanger is arranged on the discharge pipe, and one end of the flue gas output channel, which penetrates out of the low-temperature area, passes through the heat exchanger and then is connected with the absorption tower.
By adopting the technical scheme, part of heat of the flue gas input into the absorption tower can be exchanged into the flue gas in the discharge pipe, so that the temperature of the flue gas is reduced from more than 100 ℃ to less than 100 ℃, and the desulfurization reaction of the absorption tower is facilitated.
The invention has the following advantages:
1. the flue gas denitration system can save the installation of a flue gas heating device and a flue gas cooler, thereby saving energy consumption, being beneficial to environmental protection and reducing the operation cost;
2. the flue gas input channel is provided with a first temperature switch device and a second temperature switch device so as to stabilize the temperature of the flue gas conveyed to the high-temperature electric dust collector and the SCR reactor by the flue gas input channel, and the temperature of the flue gas is more beneficial to the denitration reaction of the SCR reactor;
3. flue gas analyzer and dilution fan are arranged to reduce NH4HSO4Thereby reducing NH4HSO4Corroding a catalyst metal support frame and a low-temperature area of the air preheater, and reducing the probability of blockage of the air preheater;
4. the arrangement of the air heater is beneficial to reducing the probability of low-temperature corrosion of the air preheater.
Drawings
FIG. 1 is a flow diagram of denitration in the prior art;
FIG. 2 is a schematic flow chart of the present invention;
FIG. 3 is a connection diagram of parts at the air preheater;
FIG. 4 is a connection diagram of components within the first temperature switch device;
fig. 5 is a connection diagram of components in the second temperature switch device.
Reference numerals: 1. an air preheater; 11. a dust remover; 12. a flue gas heating device; 13. an SCR denitration reactor; 14. a flue gas cooler; 2. an air preheater; 21. a high temperature zone; 22. a medium temperature zone; 23. a low temperature zone; 3. a flue gas input channel; 31. a first transfer tube; 32. a second transfer pipe; 33. a first temperature switching device; 331. a first temperature sensor; 332. a first controller; 333. a first electrically operated valve; 34. a second temperature switching device; 341. a second temperature sensor; 342. a second controller; 343. a second electrically operated valve; 35. a first safety valve; 36. a second relief valve; 37. a high-temperature electric dust remover; 4. a warm air blower; 41. an air intake section; 42. an air outlet section; 5. an SCR reactor; 51. an ammonia injection grid; 52. a catalyst; 53. a flow equalizing plate; 54. a flue gas analyzer; 55. a flue gas output channel; 6. mixing the mother pipes; 61. a dilution fan; 62. a connecting pipe; 621. connecting the electric valve; 7. an absorption tower; 71. a heat exchanger; 72. a discharge pipe; 73. a demister; 74. a circulation pipe; 741. circulating spray heads; 75. a circulation pump; 8. an induced draft fan; 9. and (4) a chimney.
Detailed Description
The invention is further described with reference to the accompanying drawings.
A flue gas denitration system, referring to figure 2, comprises a flue gas input channel 3, an air preheater 2, a high-temperature electric dust remover 37, an SCR reactor 5, a flue gas output channel 55, an absorption tower 7 and a chimney 9. The air preheater 2, the high-temperature electric dust remover 37 and the SCR reactor 5 are sequentially connected to the flue gas input channel 3.
Referring to fig. 2 and 3, the air preheater 2 is sequentially divided into a high temperature zone 21, a medium temperature zone 22, and a low temperature zone 23, and the low temperature zone 23 is adjacent to the fan heater. One end of the flue gas output channel 55 is connected to the output end of the SCR reactor 5, and the other end passes through the low temperature zone 23 and is connected to the absorption tower 7. The upper part of the absorption tower 7 is connected with a discharge pipe 72, the other end of the discharge pipe 72 is connected with a chimney 9, and the discharge pipe 72 is provided with an induced draft fan 8.
Referring to fig. 2 and 3, a heat exchange air pipe is arranged in the air preheater 2, the heat exchange air pipe penetrates through the high temperature region 21, and the section of the heat exchange air pipe penetrates through the low temperature region 23, and the section of the heat exchange air pipe penetrates through the high temperature region 21, and the section of the heat exchange air pipe is an air inlet section 41, and the air inlet section 41 is connected with a fan heater 4. The gas for heat exchange enters the air preheater 2 from the gas inlet section 41 to be heated, and then leaves the air preheater 2 from the gas outlet section 42 to finish heating.
Referring to fig. 2 and 3, one end of the flue gas input channel 3 enters from the high temperature area 21 and passes through the middle temperature area 22, when the temperature of the flue gas in the air preheater 2 is reduced to between 320 ℃ and 420 ℃, the flue gas can be just led out from the middle temperature area 22 along the flue gas input channel 3, and the temperature of the flue gas is just favorable for the SCR reactor 5 to denitrate the part of the flue gas.
Referring to fig. 3 and 4, a first temperature switch device 33 is installed on the flue gas input channel 3 between the high-temperature electric dust collector 37 and the air preheater 2, and the first temperature switch device 33 includes a first temperature sensor 331, a first controller 332 and a first electric valve 333. The first temperature sensor 331 is used for detecting the temperature in the flue gas input channel 3 and transmitting a temperature signal to the first controller 332; the first controller 332 is electrically connected with the first electric valve 333, and the first controller 332 is responsive to the temperature signal of the first temperature sensor 331 and is used for controlling the opening and closing of the first electric valve 333; the flue gas input channel 3 is connected with a first transmission pipe 31, two ends of the first transmission pipe 31 are respectively connected with two ends of a first temperature switch device 33, the middle section of the first transmission pipe 31 is located in the medium-temperature region 22 and is arranged close to the high-temperature region 21, and a first safety valve 35 is installed on the first transmission pipe 31.
Referring to fig. 3 and 4, when the temperature of the flue gas in the flue gas input channel 3 is less than 320 ℃, the first temperature sensor 331 sends a temperature signal to the first controller 332, so that the first controller 332 controls the first electric valve 333 to cut off the flue gas input channel 3, the pressure in the flue gas input channel 3 increases, the first safety valve 35 opens, and the flue gas with the temperature less than 320 ℃ returns to the part of the middle temperature zone 22 close to the high temperature zone 21. Because the part of the middle temperature area 22 close to the high temperature area 21 can be used for heating the flue gas, the temperature of the flue gas is increased to be higher than 320 ℃, and then the flue gas returns to the flue gas input channel 3 and is conveyed to the high temperature electric dust collector 37 and the SCR reactor 5.
Referring to fig. 3 and 5, a second temperature switching device 34 is installed on the flue gas input channel 3 between the high temperature electric dust collector 37 and the air preheater 2, and the second temperature switching device 34 includes a second temperature sensor 341, a second controller 342, and a second electric valve 343. The second temperature sensor 341 is configured to detect a temperature in the flue gas input channel 3, and transmit a temperature signal to the second controller 342; the second controller 342 is electrically connected with the second electric valve 343, and the second controller 342 is responsive to the temperature signal of the second temperature sensor 341 and is used for controlling the opening and closing of the second electric valve 343; the flue gas input channel 3 is connected with a second transmission pipe 32, two ends of the second transmission pipe 32 are respectively connected with two ends of a second temperature switch device 34, the middle section of the second transmission pipe 32 is positioned in the middle temperature region 22 and is arranged close to the high temperature region 21, and a second safety valve 36 is installed on the second transmission pipe 32.
Referring to fig. 3 and 5, when the temperature of the flue gas in the flue gas input channel 3 is higher than 420 ℃, the second temperature sensor 341 sends a temperature signal to the second controller 342, so that the second controller 342 controls the second electric valve 343 to cut off the flue gas input channel 3, the pressure in the flue gas input channel 3 increases, the second safety valve 36 opens, and the flue gas with the temperature higher than 420 ℃ returns to the part of the middle temperature zone 22 close to the low temperature zone 23. Because the part of the middle temperature zone 22 close to the low temperature zone 23 can be used for reducing the temperature of the flue gas, the temperature of the flue gas is reduced to be below 420 ℃, and then the flue gas returns to the flue gas input channel 3 and is conveyed to the high temperature electric dust collector 37 and the SCR reactor 5.
Referring to fig. 3, since the temperature of the flue gas may often fluctuate and may cause the temperature of the flue gas output to the outside of the middle temperature zone 22 to be higher than 420 degrees celsius or lower than 320 degrees celsius, the temperature of the flue gas input into the SCR reactor 5 may be between 320 degrees celsius and 420 degrees celsius by providing the first temperature switching device 33, the second temperature switching device 34, and the like, thereby facilitating the denitration reaction of the SCR reactor 5.
Referring to fig. 2, two sets of ammonia injection grills 51 are installed at an input end of the SCR reactor 5, and the two sets of ammonia injection grills 51 are arranged along a moving direction of the flue gas in the SCR reactor 5. The SCR reactor 5 is provided with a mixing main pipe 6 beside, the mixing main pipe 6 is connected with a dilution fan 61, the mixing main pipe 6 is also connected with two connecting pipes 62, and the two connecting pipes 62 are used for respectively connecting the mixing main pipe 6 and the two groups of ammonia injection grilles 51. The ammonia injection grid 51 is used for uniformly injecting the ammonia water in the mixing main pipe 6 into the SCR reactor 5 and mixing the ammonia gas and the flue gas. Each connecting pipe 62 is provided with a connecting electric valve 621.
Referring to fig. 2, a plurality of catalyst layers 52 are installed in the SCR reactor 5, a plurality of flow equalizing plates 53 are disposed between the catalyst 52 and the ammonia injection grid 51, and the flow equalizing plates 53 are used for equalizing ammonia gas and NOXThe mixture of (a) reaches the catalyst 52 more uniformly, thereby improving the reaction quality per unit volume of the catalyst 52. A flue gas analyzer 54 is installed at one output end of the SCR reactor 5, and the flue gas analyzer 54 can detect the proportion of ammonia nitrogen in the flue gas discharged from the SCR reactor 5.
Referring to fig. 2, a heat exchanger 71 is installed on the discharge pipe 72, and the end of the flue gas output passage 55 which passes through the low temperature zone 23 passes through the heat exchanger 71 and then is connected to the absorption tower 7. Therefore, a part of heat of the flue gas before being input into the absorption tower 7 can be exchanged into the flue gas in the discharge pipe 72, so that the temperature of the flue gas is reduced from above 100 ℃ to below 100 ℃, and the desulfurization reaction of the absorption tower 7 is facilitated.
Referring to fig. 2, a circulation pipe 74 is provided on the absorption tower 7, one end of the circulation pipe 74 is connected to the bottom of the absorption tower 7, the other end is connected to the upper part of the absorption tower 7 and is connected to a circulation nozzle 741, and a circulation pump 75 is installed on the circulation pipe 74. A demister 73 is arranged in the absorption tower 7, the demister 73 is positioned above the circulation nozzle 741, and the discharge pipe 72 is communicated above the demister 73. The circulating spray-head 741 sprays ammonia suspension drops, and the ammonia suspension drops descend to perform intersection reaction with the rising flue gas, so that the sulfur removal effect is achieved.
The specific implementation process comprises the following steps: the flue gas with the temperature of more than 1000 ℃ enters the air preheater 2 through the flue gas input channel 3 to carry out heat exchange until the temperature of the flue gas is reduced to 320 ℃ to 420 ℃, and then the flue gas is just positioned in the middle temperature region 22 and can be conducted into the high-temperature electric dust remover 37 along the flue gas input channel 3 to carry out dust removal.
After the dust removal is completed, the part of the flue gas enters one input end of the SCR reactor 5 for denitration, the ammonia water in the mixing main pipe 6 enters the ammonia spraying grid 51 in the SCR reactor 5 through the connecting pipe 62, the ammonia spraying grid 51 and the flue gas jointly act to atomize the ammonia water, so that the ammonia gas and the flue gas are mixed, and the ammonia gas is conducted to the catalyst 52 for reaction under the action of the flow equalizing plate 53. In the process, the flue gas analyzer 54 can detect the proportion of ammonia nitrogen in the flue gas after reaction, so that whether the input amount of ammonia is reasonable or not can be known, and the dilution fan 61 can be controlled to introduce air into the mixing main pipe 6, dilute the concentration of ammonia gas and adjust the input amount of ammonia.
The flue gas after denitration firstly enters the low-temperature zone 23 along the flue gas output channel 55 for heat exchange, then enters the heat exchanger 71 for heat exchange, and finally is discharged into the absorption tower 7 for desulfurization treatment. The temperature of the flue gas after passing through the heat exchanger 71 is kept below 100 ℃, and the temperature of the flue gas is suitable for the desulfurization reaction of the absorption tower 7. The flue gas in the absorption tower 7 rises and contacts with the descending suspension liquid drops of ammonia, reacts and is desulfurized. The final flue gas is discharged to a chimney 9 under the action of an induced draft fan 8 and is discharged to the atmosphere through the chimney 9.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (7)
1. A flue gas denitration system comprises a flue gas input channel (3), an air preheater (2), a high-temperature electric precipitator (37), an SCR reactor (5) and a mixing main pipe (6) connected with the SCR reactor (5), wherein the air preheater (2), the high-temperature electric precipitator (37) and the SCR reactor (5) are sequentially connected to the flue gas input channel (3); the method is characterized in that: the air preheater (2) is sequentially divided into a high-temperature area (21), a medium-temperature area (22) and a low-temperature area (23), and one end of the flue gas input channel (3) enters from the high-temperature area (21) and penetrates out from the medium-temperature area (22); one output end of the SCR reactor (5) is connected with a flue gas output channel (55), and the middle section of the flue gas output channel (55) passes through a low temperature zone (23);
a first temperature switch device (33) is installed on a flue gas input channel (3) between the high-temperature electric dust remover (37) and the air preheater (2), the first temperature switch device (33) comprises a first temperature sensor (331), a first controller (332) and a first electric valve (333), the first temperature sensor (331) is used for detecting the temperature in the flue gas input channel (3) and transmitting a temperature signal to the first controller (332), and the first controller (332) responds to the temperature signal of the first temperature sensor (331) and is used for controlling the opening and closing of the first electric valve (333); the flue gas input channel (3) is connected with a first transmission pipe (31), two ends of the first transmission pipe (31) are respectively connected with two ends of a first temperature switch device (33), the middle section of the first transmission pipe (31) is positioned in the middle temperature area (22) and is arranged close to the high temperature area (21), and a first safety valve (35) is installed on the first transmission pipe (31);
a second temperature switch device (34) is installed on the flue gas input channel (3) between the high-temperature electric dust collector (37) and the air preheater (2), the second temperature switch device (34) comprises a second temperature sensor (341), a second controller (342) and a second electric valve (343), the second temperature sensor (341) is used for detecting the temperature in the flue gas input channel (3) and transmitting a temperature signal to the second controller (342), and the second controller (342) responds to the temperature signal of the second temperature sensor (341) and is used for controlling the opening and closing of the second electric valve (343); the flue gas input channel (3) is connected with a second transmission pipe (32), two ends of the second transmission pipe (32) are respectively connected to two ends of a second temperature switch device (34), the middle section of the second transmission pipe (32) is located in the middle temperature area (22) and is arranged close to the low temperature area (23), and a second safety valve (36) is installed on the second transmission pipe (32).
2. The flue gas denitration system of claim 1, wherein: and one output end of the SCR reactor (5) is connected with a flue gas analyzer (54), and the mixing main pipe (6) is connected with a dilution fan (61).
3. The flue gas denitration system of claim 2, wherein: a heat exchange air pipe is arranged in the air preheater (2), the section of the heat exchange air pipe penetrating through the high-temperature area (21) is an air outlet section (42), the section of the heat exchange air pipe penetrating through the low-temperature area (23) is an air inlet section (41), and the air inlet section (41) is connected with a fan heater (4).
4. The flue gas denitration system of claim 1, wherein: a plurality of ammonia injection grids (51) are installed in the SCR reactor (5), and a connecting pipe (62) is connected between each ammonia injection grid (51) and the mixing main pipe (6).
5. The flue gas denitration system of claim 1, wherein: and a flow equalizing plate (53) is arranged in the SCR reactor (5).
6. The flue gas denitration system of claim 1, wherein: flue gas output channel (55) extend low temperature region (23) one end and are connected with absorption tower (7), are connected with discharge pipe (72) and discharge pipe (72) on absorption tower (7) and keep away from absorption tower (7) one end and are connected with chimney (9), install draught fan (8) on discharge pipe (72).
7. The flue gas denitration system of claim 6, wherein: the heat exchanger (71) is arranged on the discharge pipe (72), and one end of the flue gas output channel (55) penetrating out of the low-temperature area (23) passes through the heat exchanger (71) and then is connected with the absorption tower (7).
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